Hewlett-packard Development Company, L.P.

Hewlett-packard Company

Purdue Research Foundation

Brent Michael Bradburn

Randall Edward Grohs

Jan Philip Allebach

Qian Lin

Brian E Hoffmann

Zuguang Xiao

Lu Wang

Allen L Frazier

Mengqi Gao

In an example, a method is described that includes dividing an input image into a plurality of strips, where each strip is smaller than a whole of the input image. A plurality of binary images is then generated, where each of the binary images corresponds to one of the strips. Connected component labeling is performed on the binary images, one binary image at a time. An object map for the input image is then generated based on the results of the connected component labeling.

Generating an object map from a plurality of binary images

Embodiments of image processing are described that include receiving source image data including a range of values having endpoints, adjusting the source image data by treating at least one subset of endpoint data differently from data having midrange values, where adjusting the source image data is performed prior to compressing the source image data, and restoring a range of values between the endpoint data values after decompressing image data to maintain the midrange data values substantially unadjusted.

Adjusting source image data prior to compressing the source image data

The invention provides a procedure that is applicable to various halftoning methods, which minimizes image distortion introduced by the halftoning process. The procedure involves maintaining specific relationships between the halftone pattern and the phase and resolution of the input image. Specifically, that the halftone pattern is designed such that it does not bias tone reproduction with respect to the location of the input image pixels&#x2014;each input pixel should be given equal weight when filtered by the halftoning process. This suggests a 1 to 1 relationship between each pixel of the input image and the corresponding tone output produced by the halftoning process. The procedure results in improved print quality, manifested by avoidance of certain types of moir&#xe9; which are commonly associated with halftoning, as well as improved reproduction of edges and image details.

Halftone method employing 1 to 1 screening

A pixel processing system receives a target pixel value and neighbor pixel values. The neighbor pixel values may correspond to eight neighbor pixels that surround a target pixel corresponding to the target pixel value. The pixel processing system determines a minimum value and a maximum value among the neighbor pixel values. If the target pixel value is less than the minimum value, then the pixel processing system increases the target pixel value. If the target pixel value is greater than the maximum value, then the pixel processing system reduces the target pixel value. In response to increasing the target pixel value, the pixel processing system may reduce the neighbor pixel values to maintain an average value. In response to reducing the target pixel value, the pixel processing system may increase the neighbor pixel values to maintain an average value.

Pixel processing system for image production

The invention provides a procedure that is applicable to various halftoning methods, which minimizes image distortion introduced by the halftoning process. The procedure involves maintaining specific relationships between the halftone pattern and the phase and resolution of the input image. Specifically, that the halftone pattern is designed such that it does not bias tone reproduction with respect to the location of the input image pixels&mdash;each input pixel should be given equal weight when filtered by the halftoning process. This suggests a 1 to 1 relationship between each pixel of the input image and the corresponding tone output produced by the halftoning process. The procedure results in improved print quality, manifested by avoidance of certain types of moir&eacute; which are commonly associated with halftoning, as well as improved reproduction of edges and image details.

Halftone employing 1 to 1 screening

The method of the invention improves the presentation of pixel data images in output documents. The method is implemented by a pipeline of image processing actions which, among others, includes an edge evaluation step wherein neighborhoods of pixel data are examined to derive edge values that are indicative of an edge presence in the respective neighborhood. Each edge value is further indicative of the intensity of the edge. The edge evaluation action further determines scaling parameters which enable later distribution of a neighborhood's center pixel tone value to subpixels that are created during a scaling action of the center pixel.

Method and apparatus for improving image presentation in a digital copier

A compression apparatus for compressing a digital image is disclosed and includes a decomposer, a transform encoder unit and a merge plane compressor. The digital image is converted by the compression apparatus into a set of tiles suitable for transform encoding. Each tile from the set is then compressed by converting the tile into a &ldquo;merge plane data string&rdquo; and an associated &ldquo;transform encoded data string&rdquo;. The merge plane data string describes only the spatial locations of the background pixels in the tile. The transform encoded data describes the tile in the frequency domain but without the spatial frequencies associated with the background pixels. One important use of the present invention is to compress digital images prior to transmitting the digital image to a printer for printing.

Image compression of background and text tiles

A computer for compressing a digital image. The computer is operable to decompose a digital image into a set of tiles and to classify certain tiles from the set as being low detail tiles. The computer is further operable to transform each tile from the set of tiles into a series of basis function coefficients to represent the tile in the frequency domain. The computer is responsive to a tile having more than four different pixel values and classified as a low detail tile by transforming the tile into a first series of basis function coefficients. The first series of basis function coefficients includes only four coefficients that have a non-zero value.

System for compression of digital images comprising low detail areas

An Adaptive Image Resolution Enhancement Technology (IRET) process and apparatus is described to improve halftone imaging by changing ordered halftone screen resolution according to the content of the image and managing these changes based on image content. The Adaptive IRET halftoning technique maximizes the artifact reducing properties of coarser ordered screens, while minimizing the loss of rendered detail in image areas having high spatial frequency. IRET may utilize a mixture of any ordered halftone screen (e.g. clustered-dot dither, line screen, etc.) to generate halftone dots with a number of levels, and any dispersed halftone screen to generate additional levels for the ordered halftone dots. For some printing technologies, it is preferable to minimize printing artifacts by generating coarser halftone screens, rather than finer halftone screens. Coarser screening, however, means that details in the image, text, and line art will not be rendered well. Adaptive IRET uses an activity index to change its ordered halftone screen resolution according to the content of the image. To render a page with a mixture of text, line art, area fill, and photograph, it is preferable to render the &ldquo;busy&rdquo; areas, such as text, line art, and edge regions in a photograph, with a higher resolution screen. On the other hand, smooth areas, such as area fill and non-edge regions in a photograph, are better rendered with a lower resolution screen.

Adaptive image resolution enhancement technology

Apparatus and method for compressing Huffman encoded data. The compression apparatus includes a string detector and a record generator. The compression apparatus operates to receive the Huffman encoded data and the length of the codewords used to generate the Huffman encoded data. The string detector then operates to detect each set of repeating strings and each non-repeating string in the encoded data. Each set of repeating strings is replaced with a record that indicates the length of the repeating string, the number of repeats and an instantiation of the repeating string. In addition, each non-repeating string is replaced with a record that indicates the length of the non-repeating string and the non-repeating string. The resulting compressed Huffman data can then be transmitted to a printer.

Apparatus and method for compressing Huffman encoded data

Image data such as text or half-tone images is compressed and decompressed. A compressor has three phases: a bit-run length phase that counts the length of each run of consecutive identical pixels; a pairs-repetition phase that compresses repeated pairs of pixel run values to one copy of the repeated pair and a repeat count; and an optional dictionary-based micro-table encoder. The micro-table, which may be used in any application calling for a least recently used (LRU) mechanism, has multiple qualification layers, with elements within a qualification layer being promoted to the next higher qualification layer upon the occurrence of a table hit for that element, and being demoted to the next lower qualification layer by being bumped by elements promoted up from below. The result is a table that is weighted both by frequency and recency of hits.

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Boise, ID, United States of America

Brent Michael Bradburn